class Solution(object):
    def getIntersectionNode(self, headA, headB):
        """
        :type head1, head1: ListNode
        :rtype: ListNode
        """
        pA, pB = headA, headB
        while pA is not pB:
            pA = pA.next if pA else headB#  如果一长的话都会返回None
            pB = pB.next if pB else headA
        return pA


